1. Field of the Invention
The present invention relates to a projector device having an illuminating optical system and more particularly to the projector device using a micormirror device, for example, a DMD (digital micromirror device) as an image display device.
The present application claims priority of Japanese Patent Application No. 2001-202692 filed on Jul. 3, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
In recent years, in projectors, projecting devices or the like, a projector device having an illuminating optical device being equipped with a DMD is generally and widely used. A conventional projector device having such a DMD is described by referring to the below drawings. FIG. 11 is a schematic block diagram showing configurations of an illuminating optical system of the conventional projector device. As shown in FIG. 11, light emitted from a light source 101 is reflected by an elliptic plane mirror 102 and is then condensed by a rod integrator 103. The condensed light, after having gone out from the rod integrator 103, is transmitted through a relay lens 104, a reflecting mirror 105, a reflecting prism 106, and a color prism 108 to a DMD 107. The light reflected by the DMD 107 is transmitted again through the color prism 108 and the reflecting prism 106 to a projection lens 109 where the light is magnified and then is projected onto a screen 110.
Challenges presented by the conventional projector device (in seeking to project a clear image onto an entire projection screen) include reduction of nonuniformity in illumination by light from a light source and high intensity of an optical output. To meet these challenges, a prism-shaped transparent member, commonly called a rod integrator, is used to enable uniform application of the above condensed light.
The rod integrator 103, as shown in FIG. 12, is fabricated by working heat-resistant silica glass having a length of xe2x80x9cLxe2x80x9d so as to have a prism-shaped configuration. Its cross section is rectangular and is similar to a shape of a projection screen and its one end serves as a light incident face 111 and its another end serves as a light outgoing face 112. Then, as shown in FIG. 13, incident light 113, which is condensed by the elliptic plane mirror 102 and is entered from the light incident face 111 at the one end of the rod integrator 103 at an incident angle of xe2x80x9cxcex1xe2x80x9d, repeats its total reflection on an inside face of the rod integrator 103 and reaches the light outgoing face 112 at another end of the rod integrator 103. The reached light is formed so to be a beam having a rectangular shape and goes out, as outgoing light 114, from the light outgoing face 112 at an outgoing light angle of xe2x80x9cxcex1xe2x80x9d being the same as the incident angle.
By using such a rod integrator, nonuniformity in illumination can be eliminated or significantly reduced by repeated total reflection of the incident light along the lengthwise direction of the rod integrator, enabling outgoing illumination to possess high uniformity. However, mere use of the rod integrator does not always lead to acquirement of high luminance outgoing light. In order to obtain outgoing light with high luminance, the output from a light source has to be made high or the number of light sources has to be made plural (see Japanese Patent Application Laid-open No. 2000-75407). However, these methods cause an increase in power consumption. Moreover, in the case of the conventional rod integrator, in order to maintain uniformity of illumination, the number of times of total reflection of incident light within the rod integrator has to be increased and, therefore, as shown in FIG. 13, there is no choice but to increase a total length xe2x80x9cLxe2x80x9d of the rod integrator 103, which interferes with achievement of a compact illuminating optical system.
In view of the above, it is an object of the present invention to provide a projector device which is capable of reducing its costs by making it possible to increase the luminance of outgoing light from a rod integrator without a simultaneous change in the output from a light source, thereby making it possible to achieve a compact illuminating optical system using a rod integrator with a shortened total length.
According to a first aspect of the present invention, there is provided a projector device including:
an illuminating optical system having a rod integrator constructed of a transparent prism-shaped member and having a rectangular cross section to collect light emitted from a light source, a relay lens through which the light fed from the rod integrator passes, a reflecting mirror through which the light fed from the relay lens passes, a reflecting prism through which the light fed from the reflecting mirror passes, a color prism through which the light fed from the reflecting prism passes, a digital micromirror device to condense light fed from the color prism, wherein light reflected by the digital micromirror device, after having passed through the color prism, the reflecting prism and a projection lens, is projected onto a screen and wherein notches each having a predetermined angle or a convex portion having a predetermined angle is formed on a side in a vicinity of a light incident face and on a side in a vicinity of a light outgoing face.
In the foregoing, a preferable mode is one wherein, in the rod integrator, notches each having a predetermined angle are formed on a side in a vicinity of a light incident face and on a side in a vicinity of a light outgoing face.
Also, a preferable mode is one wherein, in the rod integrator, notches each having a predetermined angle are formed on a side in a vicinity of a light incident face and a convex portion having a predetermined angle is formed on a side in a vicinity of a light outgoing face.
Also, a preferable mode is one wherein, in the rod integrator, a convex portion having a predetermined angle is formed on a side in a vicinity of a light incident face and notches each having a predetermined angle are formed on a side in a vicinity of a light outgoing face.
Also, a preferable mode is one wherein, in the rod integrator, convex portions each having a predetermined angle are formed on a side in a vicinity of a light incident face and on a side in a vicinity of a light outgoing face.
Also, a preferable mode is one wherein, in the rod integrator, light having passed through the rod integrator is totally reflected at an angle formed by each of notches or a convex portion mounted on a side in a vicinity of a light outgoing face and wherein a light outgoing angle is made smaller than a light incident angle.
Also, a preferable mode is one wherein, in the rod integrator, a number of times of total reflection of incident light is increased by making large an incident angle of light entering the light incident face and a total length of the rod integrator is shortened to respond to the increased numbers of times of the total reflection of incident light.
Also, a preferable mode is one wherein, a sloped line produced at an angle formed by one portion of each of the notches on a light incident side is approximately parallel to incident light and a sloped line produced at an angle formed by another portion of each of the notches is approximately perpendicular to the incident light.
Also, a preferable mode is one wherein, in the rod integrator, a sloped line produced at an angle formed by the convex portion on a light incident side is approximately parallel to incident light.
Also, a preferable mode is one wherein, in the rod integrator, a light incident face of the convex portion formed on a light incident side which serves to take in incident light is formed so as to be larger than a rectangular cross section of a prism portion and so as to be rectangular.
Also, a preferable mode is one wherein, in the rod integrator, an angle formed by each of the notches on a light outgoing side or an angle formed by the convex portion on the light outgoing side is an angle which allows incident light to be totally reflected within the rod integrator and light coming out from the rod integrator to be effectively condensed at a predetermined light outgoing angle by the digital micromirror device.
Also, a preferable mode is one wherein, in the rod integrator, by condensing incident light lying off the rectangular light incident face out of incident light entering the rod integrator having notches on a light incident side using a face of one of the notches being approximately perpendicular to the incident light to increase an amount of incident light to be taken in, luminance of outgoing light is increased.
Furthermore, a preferable mode is one wherein, in the rod integrator, by condensing incident light lying off a rectangular light incident face having a same size as of a prism-shaped rectangular cross section out of incident light entering the rod integrator having a convex portion on a light incident side using a light incident face of the convex portion being formed so as to be larger than the rectangular light incident face to increase an amount of incident light to be taken in, luminance of outgoing light is increased.
With the above configurations, since notches each having a predetermined angle or a convex portion having a predetermined angle are formed in a vicinity of a light incident face and in a vicinity of a light outgoing face of the rod integrator, it is made possible for a rod integrator to take in incident light that has lain off a rectangular light incident face of the rod integrator out of light emitted from a light source to the rod integrator and therefore it is made possible to effectively use light that has been conventionally discarded, thus enabling improvement of luminance of the projector device without increasing an output of a light source lamp. Moreover, since a light incident angle of an incident light is made large, a number of times of total reflection is increased and, therefore, even if a total length of the rod integrator is reduced, uniformity of illumination similar to that exhibited by the lengthening of the rod integrator can be maintained. Further, even if the incident angle of the incident light is made large, light can go out at a more effective light outgoing angle to the DMD and, as a result, the illuminating system of the projector device of the present invention can be made compact. The above-described effects enable the reduction of costs for such projector devices.